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View Full Version : Movable Crane out of Wood?



Spin Doctor
04-22-2005, 12:25 PM
We have all seen the use of an engine hoist for picking things out of the beds of pick ups but what about a movable A-Frame type of crane. While in my working days I used these made from steel what about wood. What would be the minimum size lumber for weights in the 1500 to 2500 pound range. This would of course have to be able to span the width of a full size pick up. Two 2x8s for the cross beam with the balance out of 2x6s or 4x4s?. Plus this would have to fit in the garage door

ibewgypsie
04-22-2005, 12:33 PM
Tree limbs was what we used to use...

Yeah, I built me a permenant A-frame with Ibeam and trolley. 10' tall, 14' wide and it spans the shop double doors.

I still would like to build something capable of lifting two tons onto a truck. AND be knock down into parts easily put up by one person.

According to the engineering book, it take a heavy Ibeam to span 8 feet and lift 2 tons in center. More than one person can put up. Deflection is a concern also. Feet must be tied together to keep unit from deforming.

we had a aframe made from Boiler tube, light, and I had a car hanging from it outside. It sits now on casters and I rate it at less than 1,000 pounds since the legs are unstable. Book says it is not good for that much weight. Meaning, it will fail eventually.

lynnl
04-22-2005, 12:48 PM
I'd think the size would be highly dependent on the species of wood used. Some well seasoned, rough sawn hickory would be my first choice, probably followed by oak.

JeffG
04-22-2005, 06:16 PM
Yes, you can do it with wood, but for this kind of application, metal is better, if only because its properties are more predictable. Wood properties vary tremendously with species, moisture content, growth pattern, how long you've left it out in the rain, and on and on. Find a copy of "The Wood Handbook" at a good library. Originally published by the US Forest Products Labratory, reprinted commercially, but I don't know if it's still available.

Evan
04-22-2005, 06:28 PM
I would make all members from at least two and preferably three members glue laminated and screwed together. This insures that if there is a weak spot in a single piece it doesn't provide a single point failure. That is the principal with glulam trusses in buildings.

Too_Many_Tools
04-22-2005, 06:34 PM
A couple of points...

First, never use a tree branch as a crane.

I have been around far too many trees that have been rotten or have dry rot or have internal defects. There are just too many ways for a tree branch to be severely weakened internally but yet look perfectly good on the outside. In my neighborhood alone, we have had four separate incidents where trees that looked good have almost caused property damage and lost of life due to using them for lifting purposes.

When using wood to build a crane, you need to remember that you are hanging the weight from one point versus spreading it over the beam like in a floor. That means that you need to overbuild the crane in respect to what you would think that you would need.

TMT

3 Phase Lightbulb
04-22-2005, 10:13 PM
I needed a small crane once so I spent around 20 mins screwing two A-frames made out of 2x4s together and suspending some winches from them.. When I was done, I just unscrewed them and re-used the 2x4s for whatever. You can make them as strong as you want and if you make them without destroying the wood, you can re-use the wood for other things afterwards.

http://www.gnuxtools.com/psychokart/dscn1919.jpg

I just used a strong pipe over the top of the A-frames, and some 8" C-clamps to hold two winches... It worked really well and only took 20 mins to make from scratch. I got really good hoisting and positioning with two winches.

http://www.gnuxtools.com/psychokart/dscn1910.jpg

-Adrian

Steve Stube
04-22-2005, 11:19 PM
What are you fitting the engine up to? Is that project done now? How about some pictures of the finished article. TIA

3 Phase Lightbulb
04-22-2005, 11:26 PM
<font face="Verdana, Arial" size="2">Originally posted by Steve Stube:
What are you fitting the engine up to? Is that project done now? How about some pictures of the finished article. TIA</font>

I call it my PsychoKart for obvious reasons. http://bbs.homeshopmachinist.net//smile.gif

Here are a bunch of pictures of it:

http://www.bbssystem.com/viewtopic.php?t=59

-Adrian

Forrest Addy
04-23-2005, 12:03 AM
If you want to build a handy lifting horse wood is a good start provided you don't try for too large a span or intend it for too heavy a load. Limit the span to what you can back a pick up under with precision - 9 feet or so between the legs and the weight to a ton or so. Any more and you have to increase the width and depth of the beam out of proportion to its convenience in handling due to weight. Erecting the thing quickly becomes a three man job.

I built a lifting horse from 12 ft 4 x 4's and a 10 ft 4 x 8 all select quarter sawn Doug fir for strength and reliability. All 4 legs were braced to the beam with 2 x 4 and the legs were strutted about 4 ft from the ground. I padded the top edge of the beam where the chain hoist was suspended by bolting on a 1 ft piece of 4" x 3/8" flat bar so the becket chain wouldn't bite into the wood.

If you intend to use the lifting horse regularly it really should be made of metal. 8" aluminum I beam and 3" sch 40 pipe are damn expensive but superior to wood and lighter to erect while being capable of greater loads. If you design well you can make the thing adjustable and easy to erect and transport.

Look at Wallace gantries

http://www.wallacecranes.com/trialum.htm

for some ideas. Notice how adjustable they are.

[This message has been edited by Forrest Addy (edited 04-23-2005).]

Steve Stube
04-23-2005, 01:33 AM
Well you named it correctly, no brakes or ejection seat. It does have quadrasound, maybe if you can't hear the crash, it won't hurt. Oh sure. Its a killer machine alright!
Thanks for the photos.

abn
04-23-2005, 02:14 AM
I found an old rigging book at the library that went through rigging with wood extensively. I don't remember much from the book as I read it more for novelty than for serious study of wood and manila...Maybe you can find something similar.

torker
04-23-2005, 07:45 AM
Spin, I believe that you will need something pretty substantial to lift that much weight with any kind of span.
For quite a few years I used a take down gantry in my shop for pulling engines etc.
I used three 2X8 pine boards, laminated with screws and glue, for the main lifting beam.
On one wall there was another laminated beam attached to it with lags. This stood up from the floor and had a pocket to hold the top/cross beam.
On the other side I had an "upside down" T with A bracing going to the bottom. This also had a pocket for the cross beam.
I'd put the cross beam into the pocket that was against the wall, lift it up and prop it with a 2X4, then slide the "upside down T" under the beam and drop the cross beam into the pocket.
I had through bolts that held it all in its final position.
Was pretty handy and could be taken down again in about ten minutes.
The cross beam was about 8 feet long, just about right for driving a vehicle under.
This was made to lift about 900 pounds maximum...like a big block chevy and transmission pulled as a single unit.
I don't believe there was much of a safety factor there. A few times a motor would catch and you'd end up with more weight than you planned.
The cross beam would start groaning and crackling.
I was always going to add a steel plate across most of the span but then I wouldn't have been able to lift it myself.
As Forrest mentioned....quarter cut fir would have been a better choice and perhaps 2X 10 or 12. But that would still have been pretty heavy to lift that high.
I used the floor joist reasoning when building this but I missed one thing...floor joisting is designed to work as a unit. The joists running beside and the flooring attached to the tops of all the joists combine to add strength.
When you just have one joist, there is really nothing to stop deflection to the sides. This is where my beam got me into trouble. If the motor/tranny started to swing it could get pretty spooky in a hurry.
My son was just getting into hot rods and was planning to pull some engines etc.
I had to go out of town to work for six months and wasn't comfortable letting him use this so I sawed it up and bought him an engine hoist to use. It was a huge old hoist that the Kenworth dealer used to use.
Worked fine but took up massive amounts of floor space.
To date, nothing has worked as well as the gantry for unloading out of the back of a truck though. It just wasn't heavy enough.
After unloading my lathe the other day I'm thinking about putting in a heavy steel "I" beam frame right around the outside of my shop doors and cementing the works into the ground.
Be careful!
Russ

[This message has been edited by torker (edited 04-23-2005).]

Your Old Dog
04-23-2005, 08:06 AM
Has anyone made a hybrid type lift? Part steel and wood. Why couldn't the top beam be a welded configuration with "box pockets" to receive the 4x4's. A 1/2 inch rod welded across the bottom in ^ fashion with a stub center support should hold anything a backyard mechanic would want.

I have used a tree limb like Gypsie but I had to lean/wedge a 2x6 under the unsupported end. It worked but I was nervous!

At present I use a a small utility trailer bed that is about 10" off the ground and a motor lift. Once the load is lifted I drive the trailer out from under it. It has worked well for some other projects around the house such as moving my shops around and yard waste.



[This message has been edited by Your Old Dog (edited 04-23-2005).]

ibewgypsie
04-23-2005, 04:23 PM
**** I was young and bulletproof (so I thought) when I used to use a oak limb to pull engines.******

I was joking. (I've had over 100 broken bones) So I might not have been that funny. I got a broken toe on the right foot right now, don't think much of it till I step or stand wrong then the telegraph messages start. Ya gotta learn to ignore the little things.



------------------
David Cofer, Of:
Tunnel Hill, North Georgia

andy_b
04-23-2005, 10:07 PM
i made a tripod of three 12' 4x4 pieces of pressure treated lumber. i welded up metal cages about 10" long to fit over the ends of the 4x4s, and they each have a tab sticking out. the tabs all come together in the center at the peak and i put a 5/8" bolt through them to hold them together. i've used it to lift a bit over 1000# and i back my truck under it. it just clears the sides of the bed.

i've never noticed any flexing or problems, but i wouldn't stand under the thing, that's for sure.

i was just thinking about it a day or so ago and i think i am going to weld the three 10" cages into a single unit, and just stick the 4x4s into it when i need to set it up. that removes one failure point (the 5/8" bolt) and makes setup a bit easier (you don't have to find a friend to help hold the three pieces together while you try to stick the bolt through the three tabs).

use this idea at your own risk. i can't be responsible if it collapses on you or your vehicle.

andy b.

lklb
04-24-2005, 06:49 AM
<font face="Verdana, Arial" size="2"> i made a tripod of three 12' 4x4 pieces of pressure treated lumber....................... i've used it to lift a bit over 1000# and i back my truck under it. it just clears the sides of the bed. </font>

Andy B. ,that's a hell of a good idea. Maybe some simple 1" flat bar strapping the bottom of the tripod would guarantee that the legs wouldn't spread out and give an extra safety margin.
Anybody got an idea of the load capacity of Andy's contraption? I have to move a bunch of machinery out of my garage and bring it to my other house and to my shop. Building 3 of these gizmos would save a lot of time and some $$$ .
I like that idea..........elegant and simple..

ibewgypsie
04-24-2005, 09:55 AM
gin poles used to be the same, in a barn a piece of hickory or good wood with a iron end on it. Makes the end much stronger. IN my old shop I had 12"x 1/8" wraps around 4x4 posts to support a 12" ibeam in the ceiling. I welded them around the posts. Nailed them with a hundred nails.

Wood that is structurally sound will hold enourmous weight for it's given weight per strength. Unfortunatly, there is not a true consistiency. Metal is uniform. It is not allowed to deflect much strengh can be had. even a 24" I beam will deflect.

THE URL Forrest posted I printed the page out. Having the measurements can help make your own.

OUR aframe at the shop like I said is made of boiler tube, thicker than exhaust tubing but thinner than waterpipe. A double rail top with sheetmetal zig-zags. WHen it was outside it was much stronger, the legs buried up in the ground anchoring themselves. Inside the legs on the "rollers" skate around making themselves much weaker. With a proper legs design, a thin pipe or double 2x12's would hold much. I have lifted engines with 2x4's. A good one or a bad one will show itself thou.

The boiler tube aframe weighs less than 200 pounds. You can Mig the thin tubing and get proper penetration. If I worked a job where I had ready access to the boiler tube I'd come up with a good design. It was made to lift a electric motor where a crane has no access.

Even with a Ibeam in the ceiling you worry. I keep expecting to pull the ceiling down in my shop. I have the Ibeam sitting on the double 2x12's over the shop double door with a foot cut in it and bolted to the wall, going across the bay it is too short to go to other wall but has a 2x4 rect tubing legs that go out to interior walls and rest on them. One of the interior walls was tore out when the big lathe fell over as I was moving it by myself. It didn't fall then.. so? Am I lucky or a good engineer? Sometimes that is the question.

Large diameter tubing is much stronger per weight than ibeam. Ibeam is designed to accept a directional load against the web, turn a long one sideways and you bend it.

Whatever you build, perodically test it before trusting it.

BWS
04-24-2005, 10:12 PM
Dig around and see if you can come up with a website(I have their printed material)on the American Plywood Assoc......you're looking for plywood beams.Much usefull info.You'll be shocked at some of the impressive engineering data.

One redneck trick we use for temporary supports is Safeway metal scaffolding.You can practically pick up a small car with them.They also have wheels and can be rented fairly cheaply.We even use them for form supports for suspended concrete applications.

Just be dang carefull with whatever you decide(am sure you will),don't get hurt trying to save a cpl. hundred bucks.Best of luck,BW

Norman Atkinson
04-25-2005, 10:54 AM
So this is American progress.

The Romans did it- and if I can vaguely remember the Good Old Days, the Greeks did it to turn invading warships over.

Wow!!!!!!!!!